Field
Isotopically modified polyunsaturated fatty acids (“PUFAs”) and other modified PUFAs for treating certain diseases, particularly Wet and Dry Age-related Macular Degeneration (AMD); Retinitis Pigmentosa (RP); Diabetic Retinopathy (DR); Cataracts; and Stargardt Disease (SD).
Description of the Related Art
Oxidative stress is implicated in a wide variety of diseases such as mitochondrial diseases, neurodegenerative diseases, inborn error's of metabolism, diabetes, diseases of the eye, kidney diseases, liver diseases, and cardiac diseases. Specifically, such diseases include but are not limited to Wet and Dry Age-related Macular Degeneration (AMD); Retinitis Pigmentosa (RP); Diabetic Retinopathy (DR); Cataracts; and Stargardt Disease (SD). See, for example, U.S. Patent Application Nos.: 20110046219 and 20080275005 and the references cited therein.
While the number of diseases associated with oxidative stress are numerous and diverse, it is well established that oxidative stress is caused by disturbances to the normal redox state within cells. An imbalance between routine production and detoxification of reactive oxygen species (“ROS”) such as peroxides and free radicals can result in oxidative damage to cellular structures and machinery. Under normal conditions, potentially important sources of ROSs in aerobic organisms is the leakage of activated oxygen from mitochondria during normal oxidative respiration. Additionally, it is known that macrophages and enzymatic reactions also contribute to the generation of ROSs within cells. Because cells and their internal organelles are lipid membrane-bound, ROSs can readily contact membrane constituents and cause lipid oxidation. Ultimately, such oxidative damage can be relayed to other biomolecules within the cell, such as DNA and proteins, through direct and indirect contact with activated oxygen, oxidized membrane constituents, or other oxidized cellular components. Thus, one can readily envision how oxidative damage may propagate throughout a cell give the mobility of internal constituents and the interconnectedness of cellular pathways.
Lipid-forming fatty acids are well-known as one of the major components of living cells. As such, they participate in numerous metabolic pathways, and play an important role in a variety of pathologies. Polyunsaturated Fatty Acids (“PUFAs”) are an important sub-class of fatty acids. An essential nutrient is a food component that directly, or via conversion, serves an essential biological function and which is not produced endogenously or in large enough amounts to cover the requirements. For homeothermic animals, the two rigorously essential PUFAs are linoleic (cis,cis-9,12-Octadecadienoic acid; (9Z,12Z)-9,12-Octadecadienoic acid; “LA”; 18:2; n-6) and alpha-linolenic (cis,cis,cis-9,12,15-Octadecatrienoic acid; (9Z,12Z,15Z)-9,12,15-Octadecatrienoic acid; “ALA”; 18:3; n-3) acids, formerly known as vitamin F (Cunnane S C. Progress in Lipid Research 2003; 42:544-568). LA, by further enzymatic desaturation and elongation, is converted into higher n-6 PUFAs such as arachidonic (AA; 20:4; n-6) acid; whereas ALA gives rise to a higher n-3 series, including, but not limited to, eicosapentaenoic acid (EPA; 20:5; n-3) and docosahexaenoic (DHA; 22:6; n-3) acid (Goyens P L. et al. Am. J. Clin. Nutr. 2006; 84:44-53). Because of the essential nature of certain PUFAs or PUFA precursors, there are many known instances of their deficiency and these are often linked to medical conditions. Furthermore, many PUFA supplements are available over-the-counter, with proven efficiency against certain ailments (See, for example, U.S. Pat. No. 7,271,315 and U.S. Pat. No. 7,381,558).
PUFAs endow mitochondrial membranes with appropriate fluidity necessary for optimal oxidative phosphorylation performance. PUFAs also play an important role in initiation and propagation of the oxidative stress. PUFAs react with ROS through a chain reaction that amplifies an original event (Sun M, Salomon R G, J. Am. Chem. Soc. 2004; 126:5699-5708). However, non-enzymatic formation of high levels of lipid hydroperoxides is known to result in several detrimental changes. Indeed, Coenzyme Q10 has been linked to increased PUFA toxicity via PUFA peroxidation and the toxicity of the resulting products (Do T Q et al, PNAS USA 1996; 93:7534-7539). Such oxidized products negatively affect the fluidity and permeability of their membranes; they lead to oxidation of membrane proteins; and they can be converted into a large number of highly reactive carbonyl compounds. The latter include reactive species such as acrolein, malonic dialdehyde, glyoxal, methylglyoxal, etc. (Negre-Salvayre A, et al. Brit. J. Pharmacol. 2008; 153:6-20). But the most prominent products of PUFA oxidation are alpha, beta-unsaturated aldehydes such as 4-hydroxynon-2-enal (4-HNE; formed from n-6 PUFAs like LA or AA), 4-hydroxyhex-2-enal (4-HHE; formed from n-3 PUFAs like ALA or DHA), and corresponding ketoaldehydes (Esterfbauer H, et al. Free Rad. Biol. Med. 1991; 11:81-128; Long E K, Picklo M J. Free Rad. Biol. Med. 2010; 49:1-8). These reactive carbonyls cross-link (bio)molecules through Michael addition or Schiff base formation pathways, and have been implicated in a large number of pathological processes (such as those introduced above), age-related and oxidative stress-related conditions, and aging. Importantly, in some cases, PUFAs appear to oxidize at specific sites because methylene groups of 1,4-diene systems (the bis-allylic position) are substantially less stable to ROS, and to enzymes such as cyclogenases and lipoxygenases, than allylic methylenes.
We have now discovered that oxidation resistant PUFAs, PUFA mimetics, PUFA pro-drugs and/or fats containing oxidation resistant PUFAs and PUFA mimetics are useful for mitigating and/or treating oxidative retinal diseases.